Additive manufacturing system and method

ABSTRACT

An additive manufacturing (AM) system includes a housing defining a chamber and a build platform disposed in a lower portion of the chamber. The AM system includes an upper gas inlet disposed in a side-wall and in an upper portion of the chamber and configured to supply an upper gas flow parallel to the build platform. The AM system includes a lower gas inlet in the lower portion of the chamber, wherein the lower gas inlet includes one or more pairs of dividing walls extending from the side-wall toward the build platform and configured to guide the lower gas flow at one or more flow angles with respect to the build platform. The AM system includes at least one gas delivery mechanisms to regulate flow characteristics of the upper and lower gas flows, and includes a gas outlet to discharge the upper and lower gas flows from the chamber.

BACKGROUND

The subject matter disclosed herein generally relates to an additivemanufacturing system and method, and more specifically, to an additivemanufacturing system and method that employs focused energy toselectively fuse a powder material to produce an object.

Additive manufacturing (AM) processes generally involve the buildup ofone or more materials to make a net or near-net shape object, incontrast to subtractive manufacturing methods, which selectively removematerial from an initial form to fabricate an object. Though “additivemanufacturing” is an industry standard term (ASTM F2792), it encompassesvarious manufacturing and prototyping techniques known under a varietyof names, including freeform fabrication, 3D printing, rapidprototyping/tooling, etc. A particular type of AM process uses a focusedenergy source (e.g., an electron beam, a laser beam) to sinter or melt apowder material deposited on a build platform within a chamber, creatinga solid three-dimensional object in which particles of the powdermaterial are bonded together.

Laser sintering/melting, as used in Direct Laser Sintering (DLS) and/orDirect Laser Melting (DLM), is a common industry term used to refer toproducing three-dimensional (3D) objects by using a laser beam to sinteror melt a fine powder. In particular, laser sintering/melting techniquesoften entail projecting a laser beam onto a controlled amount of powder(e.g., a powder bed) on a substrate, so as to form a layer of fusedparticles or molten material thereon. When the laser beam interacts withthe powder at a powder bed, smoke and/or a particulate matter (e.g.,condensate, spatter) is produced within the chamber. The smoke and/orthe particular matter may be detrimental to the quality of the resultingobject. As an example, the suspended smoke and/or particular matterwithin the chamber can interfere with the laser beam and reduce theenergy or intensity of the laser beam before it reaches the powder bed.As another example, the smoke and/or the particular matter may depositonto the powder bed and may become incorporated into the resultingobject.

In certain laser sintering/melting (or DLS/DLM) systems, a gas flow isintroduced in an upper portion of the chamber (e.g., toward the top ofthe chamber in the z-direction and away from the build platform) to flowgenerally parallel to the build platform in an attempt to remove thesmoke and/or particulate matter and prevent deposition. However, thisupper gas flow may not efficiently remove the smoke and/or particulatematter in the lower portion of the chamber (e.g., toward the buildplatform and away from the top of the chamber in the z-direction). Inaddition, the upper gas flow may entrain gas from the chamber resultingin a chaotic flow with large areas of recirculation within the chamber.This chaotic flow may trap or deposit the particulate matter in variousparts of the chamber, which can lower the quality of the resultingobject of the DLS/DLM processes.

BRIEF DESCRIPTION

In one embodiment, an additive manufacturing (AM) system includes ahousing defining a chamber, a build platform disposed in a lower portionof the chamber, and a powder application device configured to deposit abed of powder material on the build platform. The AM system includes anupper gas inlet disposed in a first side-wall and in an upper portion ofthe chamber and configured to supply an upper gas flow parallel to thebuild platform. The AM system includes a lower gas inlet in a lowerportion of the chamber, wherein the lower gas inlet includes one or morepairs of dividing walls extending from the first side-wall towards thebuild platform and configured to guide the lower gas flow at one or moreflow angles with respect to the build platform. The AM system includesone or more gas delivery mechanisms coupled to the upper and lower gasinlets and configured to regulate one or more flow characteristics ofthe upper and lower gas flows. The AM system also includes a gas outletdisposed in a second side-wall of the chamber, opposing the firstside-wall, wherein the gas outlet is configured to discharge the upperand lower gas flows from the chamber.

In another embodiment, a method of operating an additive manufacturingsystem includes depositing a bed of a powder material on a buildplatform within a chamber. The method includes supplying an upper gasflow into the chamber horizontally above the build platform andsupplying a lower gas flow into the chamber towards the build platform.The method also includes applying a focused energy beam to at least aportion of the bed of the powder material deposited on the buildplatform to form a solidified layer.

In another embodiment, an additive manufacturing (AM) system includes ahousing defining a chamber, a build platform disposed in the chamber,and a powder application device arranged in the chamber and configuredto dispose a bed of powder material onto the build platform. The AMsystem includes an energy generating system arranged in the chamber andconfigured to generate and direct a focused energy beam onto at least aportion of the bed of powder material. The AM system includes apositioning system coupled to the build platform, the energy generatingsystem, the powder application device, or a combination thereof, andconfigured to move the build platform, the energy generating system, thepowder application device, or a combination thereof, relative to oneanother. The AM system includes an upper gas inlet disposed in a firstside-wall and in an upper portion of the chamber and configured tosupply an upper gas flow parallel to the build platform. The AM systemincludes a lower gas inlet in a lower portion of the chamber, whereinthe lower gas inlet comprises one or more pairs of dividing wallsextending from the first side-wall towards the build platform andconfigured to guide the lower gas flow at one or more flow angles withrespect to the build platform. The AM system includes one or more gasdelivery mechanisms coupled to the upper and lower gas inlets andconfigured to regulate one or more flow characteristics of the upper andlower gas flows. The AM system also includes a gas outlet, disposed in asecond side-wall of the chamber, opposing the first side-wall, whereinthe gas outlet is configured to discharge the upper and lower gas flowsfrom the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a schematic diagram of an embodiment of an additivemanufacturing (AM) system having a manufacturing chamber, in accordancewith present embodiments;

FIG. 2 is a schematic perspective view illustrating an embodiment of themanufacturing chamber of the AM system of FIG. 1 having both an uppergas flow arrangement and a lower gas flow arrangement having dividingwalls configured to guide the lower gas flow, in accordance with presentembodiments;

FIG. 3 is a cross-sectional schematic diagram of an embodiment of thedividing walls of the AM system of FIG. 2 having relatively weak nozzleeffects, in accordance with present embodiments;

FIG. 4 is a cross-sectional schematic diagram of an embodiment of thedividing walls of the AM system of FIG. 2 having relatively strongnozzle effects, in accordance with present embodiments;

FIG. 5 is a cross-sectional schematic diagram of an embodiment of thedividing walls of the AM system of FIG. 2 configured to guide the lowergas flow into multiple streams having generally the same shape, inaccordance with present embodiments;

FIG. 6 is a cross-sectional schematic diagram of another embodiment ofthe dividing walls of the AM system of FIG. 2 configured to guide thelower gas flow into multiple streams having different shapes, inaccordance with present embodiments; and

FIG. 7 is a flow chart of an embodiment of a method for operating the AMsystem of FIG. 2, in accordance with present embodiments.

DETAILED DESCRIPTION

One or more specific embodiments of the present disclosure will bedescribed below. In an effort to provide a concise description of theseembodiments, all features of an actual implementation may not bedescribed in the specification. It should be appreciated that in thedevelopment of any such actual implementation, as in any engineering ordesign project, numerous implementation-specific decisions must be madeto achieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

In the following specification and the claims, the singular forms “a”,“an” and “the” include plural referents unless the context clearlydictates otherwise. As used herein, the term “or” is not meant to beexclusive and refers to at least one of the referenced components beingpresent and includes instances in which a combination of the referencedcomponents may be present, unless the context clearly dictatesotherwise. The term “uniform gas flow”, as used herein, means that theflow velocity of a gas flow does not significantly vary across a path ofthe gas flow. As used herein, the term “additive manufacturing”, relatesto any suitable laser sintering/melting additive manufacturingtechnique, including, but are not limited to: Direct Metal LaserMelting, Direct Metal Laser Sintering, Direct Metal Laser Deposition,Laser Engineered Net Shaping, Selective Laser Sintering, Selective LaserMelting, Selective Heat Sintering, Fused Deposition Modeling, HybridSystems, or combinations thereof.

The present disclosure generally encompasses systems and methods forfabricating objects using a laser sintering/melting-based method ofadditive manufacturing. As mentioned, for such additive manufacturingtechniques, when the laser beam sinters or melts the powder bed withinan enclosed manufacturing chamber, smoke and/or particulate matter(e.g., condensate, spatter) is can accumulate within the chamber. Asmentioned, this smoke and/or the particular matter may interact with thelaser beam and/or the object being printed and interfere with thefabrication process. As such, it may be desirable to remove the smokeand/or the particular matter from the chamber to improve manufacturingprocess and/or the quality of the resulting object.

As discussed in detail below, some embodiments of the present disclosurepresent additive manufacturing (AM) systems and methods that employ acombination of an upper gas flow in an upper portion of the chamber anda lower gas flow in a lower portion of the chamber, wherein the lowergas flow is generally directed toward the build platform. The additionof the lower gas flow may advantageously overcome the above notedshortcomings of an AM system having only the upper gas flow by moreefficiently removing the smoke and/or particulate matter from thechamber, as well as suppressing entrainment and recirculation of thesmoke and/or the particulate matter inside the chamber of the AM system.As such, the stagnation and/or deposition of the smoke and/orparticulate matter on various locations inside the chamber may besubstantially reduced or eliminated, and thus may lead to improvedquality of the resulting object of the AM process. In some embodiments,the lower gas flow may include multiple streams having different flowcharacteristics. The flow characteristics may include flow distribution,flow rate (e.g., mass flow rate, volume flow rate), flow velocity (e.g.,in meters per second (m/s)), flow direction or angle, flow temperature,or any combination thereof. The flow velocities and/or other flowcharacteristics of the multiple streams may be controlled or tuned todesirable levels to interface with the upper gas flow. The controlled ortuned velocity gradients (and/or gradients in terms of other flowcharacteristics) may substantially reduce or eliminate the gasentrainment, which in turn, may enhance the efficiency of removing thesmoke and/or particulate matter from the chamber.

FIG. 1 illustrates an example embodiment of an AM system 10 (e.g., alaser sintering/melting AM system 10) for producing an article or objectusing a focused energy source or beam. In the illustrated embodiment,the AM system 10 includes a controller 12 having memory circuitry 14that stores instructions (e.g., software, applications), as well asprocessing circuitry 16 configured to execute these instructions tocontrol various components of the AM system 10. The AM system 10includes a housing 18 defining a manufacturing chamber 20 (also referredto herein as chamber 20) having a volume. The chamber 20 is sealable tocontain an inert atmosphere and to protect the build process from theambient atmosphere. The AM system 10 includes a build platform 22disposed inside the chamber 20 on a base portion or bottom-wall 24 ofthe housing 18. In some embodiments, the build platform 22 may have aworking area (e.g., the top surface of the build platform 22) in a rangebetween about 0.01 square meters (m²) and about 1.5 m². The article orobject of the AM process is fabricated on the build platform 22, asdiscussed below.

The AM system 10 includes a powder application device 26, which may bearranged inside the chamber 20 to deposit a quantity (e.g., a layer orbed) of a powder material onto the build platform 22. The powdermaterial deposited on the build platform 22 generally forms a powder bed28. The powder material may include, but is not limited to, polymers,plastics, metals, ceramics, sand, glass, waxes, fibers, biologicalmatter, composites, or hybrids of these materials. These materials maybe used in a variety of forms as appropriate for a given material andmethod, including for example without limitation, solids, powders,sheets, foils, tapes, filaments, pellets, wires, atomized, andcombinations of these forms.

The AM system 10 includes an energy generating system 30, which may bearranged inside the chamber 20 for generating and selectively directinga focused energy beam 31, such as laser, onto at least a portion of thepowder bed 28 disposed on the build platform 22. For the embodimentillustrated in FIG. 1, the energy generating system 30 is arranged inproximity to a top portion or top-wall 32 of the housing 18, opposite tothe base portion or the bottom-wall 24. The powder bed 28 disposed onthe build platform 22 is subjected to the focused energy beam 31 in aselective manner as controlled by the controller 12, depending on thedesired geometry of the article. In some embodiments, the energygenerating system 30 includes a focused energy source for generating thefocused energy beam 31. In some embodiments, the focused energy sourceincludes a laser source and the focused energy beam 31 is a laser beam.In some embodiments, the laser source includes a pulsed laser sourcethat generates a pulsed laser beam. The pulsed laser beam is not emittedcontinuously, in contrast with a continuous laser radiation, but isemitted in a pulsed manner e.g., in time limited pulses with interval.In some embodiments, the energy generating system 30 includes aplurality of focused energy sources that is configured to selectivelyirradiate the powder bed 28 using the focused energy beam 31.

The AM system 10 includes a positioning system 36 (e.g., a gantry orother suitable positioning system), which may be arranged inside thechamber 20. The positioning system 36 may be any multidimensionalpositioning system, such as a delta robot, cable robot, robot arm, oranother suitable positioning system. The positioning system 36 may beoperatively coupled to the powder application device 26, the energygenerating system 30, the build platform 22, or a combination thereof.The positioning system 36 may move the powder application device 26, theenergy generating system 30, the build platform 22, or a combinationthereof, relatively to one another, in any of the x-, y-, andz-directions, or a combination thereof.

The AM system 10 is further configured to supply an upper gas flow and alower gas flow into the chamber 20 and discharge a gas flow from thechamber 20, as will be discussed in FIG. 2. The gas flow beingdischarged from the chamber 20 includes the upper gas flow, the lowergas flow, as well as a substantial portion of any smoke and/orparticulate matter that is generated on application of the focusedenergy beam 31 to selectively melt or sinter the powder bed 28 duringforming of desired article. By employing a combination of the upper andlower gas flows, gas entrainment and recirculation of the smoke and/orparticulate matter may be substantially reduce or eliminated,substantially improving the quality of the build process and/or thearticle being printed.

FIG. 2 is a schematic perspective view illustrating an embodiment of thechamber 20 of the AM system 10, in accordance with present embodiments.As illustrated, the AM system 10 includes an upper gas flow system 40arranged in an upper portion 42. In some embodiments, the upper portion42 may include upper 50%, upper 60%, upper 70%, or upper 80% in thez-direction of the chamber 20. The upper gas flow system 40 may beintegrated with and/or coupled to the housing 18. The upper gas flowsystem 40 includes an upper gas inlet 44 for supplying an upper gas flow46 to the chamber 20. For the illustrated embodiment, the upper gasinlet 44 includes a plurality of openings 48 in a side-wall 50 of thehousing 18. The plurality of openings 48 may include an array ofopenings that allow the upper gas flow 46 to flow substantiallyuniformly along a direction 68 (e.g., parallel to the x-direction,parallel to a top 70 surface of the build platform 22, perpendicular tothe z-direction). The plurality of openings 48 may be of any suitableshape and size that enable substantially uniform gas flow. In someembodiments, the plurality of openings 72 may be in the form of circularholes, as illustrated in FIG. 2. In some embodiments, the upper gasinlet 44 may include only one opening having any suitable shape.Further, the upper gas inlet 44 may be coupled to an upper gas deliverymechanism 74 that is in turn, coupled to a gas supply line. The uppergas delivery mechanism 74 may help uniformly supply the upper gas flow46 through an entire length 76 of the chamber 20.

The embodiment of the AM system 10 shown in FIG. 2 also includes a lowergas flow system 80 arranged in a lower portion 82. In some embodiments,the lower portion 82 may include lower 50%, lower 40%, lower 30%, orlower 20% in the z-direction of the chamber 20. The lower gas flowsystem 80 may be integrated with and/or coupled to the housing 18. Thelower gas flow system 80 includes lower gas inlet 84 for supplying alower gas flow 86 to the chamber 20. For the illustrated embodiment, thelower gas inlet 84 is defined by dividing walls 88 (e.g., an upperdividing wall 90 and a lower dividing wall 92) extending in they-direction from a side-wall 94 to a side-wall 96 of the housing 18,through the entire width 98 of the chamber 20. The illustrated dividingwalls 88 also extend in the x-direction from the side-wall 50 toward aside-wall 100 of the housing 18 through a least a portion of the length76 of the chamber 20. The lower gas inlet 84 is arranged such that thelower gas flow 86 is guided between the dividing walls 88 to flow towardthe build platform 22. The dividing walls 88 are arranged such that thelower gas flow 86 exits at a lower gas outlet 102 that is in closeproximity to the build platform 22. In some embodiments, the lower gasoutlet 102 may be about 50 centimeter (cm) to about 0.5 cm, about 30 cmto about 0.5 cm, about 20 cm to about 0.5 cm, about 20 cm, or about 10cm to about 0.5 cm to the build platform 22 (e.g., in the z-direction).The lower gas flow 86 exiting the lower gas inlet 84 flows generallyuniformly along the direction 68 (e.g., parallel to the x-direction,parallel to a top 70 surface of the build platform 22, perpendicular tothe z-direction).

Furthermore, the lower gas inlet 84 is arranged, such that the presenceof the dividing walls 88 does not interfere with movements andoperations of the various components of the AM system 10. For example,the presence of the dividing walls 88 does not interfere with movements(e.g., in the x-, y-, z-direction or a combination thereof) andoperations of the powder application device 26. In some embodiments, thedividing walls 88 may be arranged above (e.g., in the z-direction) thepowder application device 26 (shown in FIG. 1). In some embodiments, thelower gas outlet 102 may be adjacent (e.g., in the x-direction) and inclose proximity (e.g., within about 30 cm to about 20 cm, about 25 toabout 15 cm, or about 20 cm) to an edge 104 of the build platform 22. Insome embodiments, the lower gas outlet 102 may be slightly above (e.g.,in the z-direction) and in close proximity (e.g., about 50 cm to about0.5 cm, about 30 cm to about 0.5 cm, about 20 cm to about 0.5 cm, about20 cm, or about 10 cm to about 0.5 cm to the build platform 22) to theedge 104 of the build platform 22.

In some embodiments, the lower gas inlet 84 may include more than twodividing walls 88 (e.g., 3, 4, 5, 6, 7, 8, or any suitable numbers)adjacent to one another in the z-direction such that the lower gas flow86 may include multiple (e.g., 2, 3, 4, 5, 6, 7, or any suitablenumbers) streams. The multiple streams exiting the lower gas inlet 84may flow generally uniformly along the direction 68 (e.g., parallel tothe x-direction, parallel to a top 70 surface of the build platform 22,perpendicular to the z-direction). The lower gas inlet 84 may be coupledto a lower gas delivery mechanism 106 that is in turn, coupled to a gassupply line. The lower gas delivery mechanism 106 may help uniformlysupply the lower gas flow 86 through a significant portion of the entirelength 76 of the chamber 20.

The AM system 10 as shown in FIG. 2, also includes a gas outlet 108 fordischarging a gas flow 110 from the chamber 20. The discharged gas flow110 may include the upper gas flow 46, the lower gas flow 86, as well asa substantial portion of any smoke and/or particulate matter that isgenerated during the AM process. In the illustrated embodiment, the gasoutlet 108 is arranged at the side-wall 100 of the housing 18, opposingthe side-wall 50 where the upper and lower gas flows 46 and 86 enter thechamber 20. The gas outlet 108 may be arranged toward the upper portionof the side-wall 100 such that the upper gas flow 46 travels directly,tangentially above the build platform 22. In some embodiments, the upperportion of the side-wall 100 may include upper 50%, 40%, 30%, 20%, or10% of the side-wall 100. While the gas outlet 108 is illustrated asbeing circular in shape in FIG. 2 for simplicity, the gas outlet 108 canbe of any suitable shape (e.g., rectangular, polygon, oval) that enablessufficient discharging of the gas flow 110. In some embodiments, the gasoutlet 108 may include a plurality of openings on the side-wall 100 todischarge the gas flow 110. The gas outlet 44 may be coupled to asuction mechanism to draw and discharge the gas flow 110 from thechamber 20.

For the illustrated embodiment, the AM system 10 also includes a flowconditioning device 112 configured to help regulating flowcharacteristics of the upper gas flow 46 and the lower gas flow 86. Theflow characteristics may include flow distribution, flow rate (e.g.,mass flow rate, volume flow rate), flow velocity (e.g., in meters persecond (m/s)), flow direction or angle, flow temperature, or anycombination thereof. For example, the flow conditioning device 112 maybe disposed within the housing 18 (e.g., to form fit the inner walls ofthe housing 18, extending from the top-wall 32 to the bottom-wall 24 ofthe housing 18 in the z-direction and/or extending from the side-wall 94to the side-wall 96 of the housing 18 in the y-direction) adjacent tothe upper and lower gas inlets 44 and 84, such that the upper and lowergas flows 46 and 86 pass through separate portions of the flowconditioning device 112 before flowing over the build platform 22 asdescribed above. The flow characteristics of the upper and lower gasflows 46 and 86 are separately conditioned by the flow conditioningdevice 112 to desired levels for removing the smoke and/or particulatematter (e.g., condensate, spatter) from the chamber 20. For example, theflow conditioning device 112 may have a plurality of openings 114extending through a thickness 116 (e.g., any suitable value). Theplurality of openings 112 may be arranged and shaped (e.g.,honeycomb-like structure, sponge-like structure) to allow the upper andlower gas flows 46 and 86 passing through the thickness 116 andcondition the flow characteristics of the upper and lower gas flows 46and 86 in desired ranges (e.g., the flow characteristics are influencedby the sizes, shapes, and/or arrangements of the plurality of openings114). In some embodiments, the flow conditioning device 112 may beomitted.

The upper gas flow 46 and the lower gas flow 86 include inert gas (e.g.,argon, nitrogen, or the like, or a combination thereof). The upper andlower gas flows 46 and 86 may be supplied to the chamber 20 via theupper and lower gas delivery mechanisms 74 and 106, respectively,including one or more suitable conveying devices and/or flow regulatingdevices such as, one or more fluid valves 73 and 105, one or more pumpsor blowers 75 and 107, or a combination thereof. In some embodiments,the upper and lower gas delivery mechanisms 76 and 106 may be the samegas delivery mechanism (e.g., the one or more pumps or blowers 75 and107 are the same pumps or blowers delivering the upper and lower gasflows 46 and 86 to the upper and lower gas inlets 44 and 84, the one ormore fluid valves 73 and 105 are the same fluid valves regulating theupper and lower gas flows 46 and 86 prior to entering the upper andlower gas inlets 44 and 84). In some embodiments, the suction mechanismcoupled to the gas outlet 108 may include a suitable filtrationmechanism to filter or treat the discharged gas flow 110 and torecirculate the filtered gas flow 110 back to the chamber 20 through theupper gas inlet 44 and/or the lower gas inlet 84.

In addition, the upper and lower gas delivery mechanisms 74 and 106 maybe operatively coupled to the controller 12, which is configured tocontrol the upper and lower gas flows 46 and 86, in addition to theremainder of the AM system 10. The controller 12 may be configured tocontrol one or more fluid flow characteristics of the upper and lowergas flows 46 and 86 to substantially reduce or eliminate gas entrainmentor chaotic gas flow within the chamber 20, such that the smoke and/orparticulate matter (e.g., condensate, spatter) may be effectivelyremoved from the chamber 20 (e.g., discharged from the chamber 20 viathe gas outlet 108). The flow characteristics may include flowdistribution, flow rate (e.g., mass flow rate, volume flow rate), flowvelocity, flow direction or angle, flow temperature, or any combinationthereof. For example, the controller 12 may control operations of theupper gas delivery mechanism 74 (e.g., the one or more fluid valves 73,the one or more pumps or blowers 75) and the lower gas deliverymechanism 106 (e.g., the one or more fluid valves 105, the one or morepumps or blowers 107) to control flow characteristics of the upper andlower gas flows 46 and 86. In some embodiments, the flow velocity of thelower gas flow 86 may be greater than the flow velocity of the upper gasflow 46. In some embodiments, the flow velocity of the lower gas flow 86may be in a range about 10 times and about 1.5 times the flow velocityof the upper gas flow 46. In some embodiments, the flow velocity of thelower gas flow 86 may be in a range about 9 times and about 7 times theflow velocity of the upper gas flow 46 the 8 times the flow velocity ofthe upper gas flow 46. In some embodiments, the flow velocity of thelower gas flow 86 may be in a range about 8 times the flow velocity ofthe upper gas flow 46. In some embodiments, the flow velocity of theupper gas flow 46 may be in a range between about 0.2 m/s and 1 m/s andthe flow velocity of the lower gas flow 86 may be in a range betweenabout 2 m/s and 5 m/s. In certain embodiments, the flow velocity of theupper and lower gas flows 46 and 86 combined may be in a range betweenabout 50 cubic meters per hour (m³/h) and about 1000 m³/h. The flowvelocity of the upper and lower gas flows 46 and 86 combined may varydepending on the volume of the chamber 20. It should be noted thatbecause the AM system 10 employs a combination of the upper and lowergas flows 46 and 86, a relatively smaller or less powerful pump orblower may be used for delivering the upper gas flow 46 (e.g., smalleror less powerful relative to the case that the AM system 10 only employsthe upper gas flow 46, not the lower gas flow 86) in certainembodiments.

As set forth above, the combination of the upper gas flow 46 and thelower gas flow 86 may help substantially reduce or eliminate gasentrainment and chaotic gas flow, and thus improve the performance andefficiency of the AM system 10 by removing smoke and/or otherparticulates generated during the AM process. FIG. 3 is a schematiccross-sectional view illustrating an embodiment of the dividing walls 88for guiding the lower gas flow 86. In the illustrated embodiment, thedividing walls 88 include the upper dividing wall 90 and the lowerdividing wall 92 configured to guide the lower gas flow 86 to flow fromthe lower gas inlet 84 toward the build platform 22 (shown in FIG. 2).The dividing walls 88 may be shaped such that the lower gas flow 86exits the lower gas outlet 102 at a flow angle 120 (e.g., with respectto the build platform 22 of FIG. 2, with respect to the x-direction).The dividing walls 88 may be made of any suitable material (e.g.,metals, alloys, plastics, composites) that has sufficient mechanicalstrength and structural integrity to maintain their shapes. In theillustrated example, the upper dividing wall 90 has a bending point 122where the upper dividing wall 90 bends at a bending angle 124 (e.g.,with respect to the x-direction) toward the build platform 22, and thelower dividing wall 92 has a bending point 126 where the lower dividingwall 92 bends at a bending angle 128 (e.g., with respect to thex-direction) toward the build platform 22. In certain embodiments, thebending angles 124 and 128 may be substantially the same, and thebending points 122 and 126 may be at about the same location (e.g., withrespect to the x-direction), such that a width 130 of the lower gas flow86 path between the upper and lower dividing walls 90 and 92 issubstantially constant along a length 132 of the dividing walls 88. Inother embodiments, the width 130 may vary (e.g., increase, decrease)along the length 132 of the dividing walls 88.

It should be noted that the shapes of the dividing walls 88 may bemodified to change the flow characteristics (e.g., flow distribution,flow rate, flow velocity, flow direction or angle, flow temperature, ora combination thereof) of the lower gas flow 86 and/or the location ofthe lower gas outlet 102 (e.g., relative to the build platform 22). Asan example, one or more parameters including the locations of thebending points 122 and 126, the bending angles 124 and 128, the width130, and the length 132 may be modified to change to the flow angle 120of the lower gas flow 86. In some embodiments, the flow angle 120 may bein a range between about 40 degrees and about 1 degree, about 25 degreesand about 1 degree, about 30 degrees and about 5 degrees, about 30degrees and about 20 degrees, and about 20 degrees and about 10 degrees.

As another example, the dividing walls 88 may be shaped to have strongnozzle effects to change or adjust the flow characteristics of the lowergas flow 86. FIG. 4 is a schematic cross-sectional view illustrating anexample of the dividing walls 88 having relatively stronger nozzleeffects, in comparison to dividing walls 88 of FIG. 3. For theillustrated embodiment, the bending angle 124 of the upper dividing wall90 is greater than the bending angle 128 of the lower dividing wall 92,such that the width 130 of the lower gas flow 86 path decreases alongthe length 132 of the dividing walls 88 toward the lower gas outlet 102,which in turn, creates relatively stronger nozzle effects to influencethe flow characteristics of the lower gas flow 86. Herein, a relativelysharper decrease in the width 130 along the length 132 toward the lowergas outlet 102 enables the relatively stronger nozzle effects. The flowvelocity and/or flow rate of the lower gas flow 86 may increase withincreasing (stronger) nozzle effects.

Furthermore, as set forth above, the lower gas inlet 84 may include morethan two dividing walls 88 adjacent to one another in the z-direction,such that the lower gas flow 86 includes multiple streams. FIG. 5 is aschematic cross-sectional view illustrating an example embodiment inwhich the dividing walls 88 are configured to guide the lower gas flow86 into multiple streams 140. In the illustrated embodiment, thedividing walls 88 include a first pair of dividing walls 142 to guide afirst stream of flow 144, a second pair of dividing walls 146 to guide asecond stream of flow 148, and a third pair of dividing walls 150 toguide a third stream of flow 152. The first pair of dividing walls 142is separated from the second pair of dividing walls 146 by a distance154 (e.g., in the z-direction) and the second pair of dividing walls 146is separated from the third pair of dividing walls 150 by a distance156. The distances 154 and 156 may be the same or different, and may beany suitable values. In some embodiments, three dividing walls 88 canform two pairs of dividing walls to guide two streams 140. While onlythree pairs of dividing walls are illustrated, the dividing walls 88 mayinclude any suitable number of pairs (e.g., 2, 3, 4, 5, 6, or more) ofdividing walls to create any suitable number (e.g., 1, 2, 4, 5, 6, ormore) of the multiple streams 140. For the illustrated embodiment, themultiple streams 140 have distinct flow paths that are generallyparallel or laminar to one another.

It should be noted that the variations in shapes and nozzle effects ofthe dividing walls 88, as discussed in FIGS. 3 and 4, are alsoapplicable to multiple pairs of dividing walls (e.g., the first, second,and third pairs of dividing walls 142, 146, and 150 of FIG. 6). In someembodiments, the multiple pairs of dividing walls 88 (e.g., the firstpair of walls 142, the second pair of walls 146, and the third pair ofwalls 150) may have substantially the same shape and/or the same nozzleeffects. In certain embodiments, the multiple pairs of dividing walls 88(e.g., the first pair of dividing walls 142, the second pair of dividingwalls 146, and the third pair of dividing walls 150) may have differentshapes and/or different nozzle effects, as illustrated in FIG. 6. Forthe illustrated embodiment, the second pair of dividing walls 146 isshaped to have stronger nozzle effects than the first pair of dividingwalls 142 and/or the third pair of dividing walls 150. In someembodiments, the multiple pairs of dividing walls 88 may be shaped, suchthat widths 143, 147, and 151 of the flow paths of the first, second,and third streams 144, 148, and 152, respectively, are different fromone another. For example, the width 147 may be greater than the width143 and/or the width 151. In some embodiments, the multiple pairs ofdividing walls 88 may be shaped such that flow angles 144, 149, and 153of the first, second, and third streams 144, 148, and 152, respectively,are different from one another. For example, the flow angle 153 may begreater than the flow angle 149 and/or the flow angle 145.

It should be noted that the multiple dividing walls 88 (e.g., the firstpair of dividing walls 142, the second pair of dividing walls 146, andthe third pair of dividing walls 150) may be shaped to collectivelychange the flow characteristics of the lower gas flow 86 in relation tothe flow characteristics of the upper gas flow 46. In particular, theflow characteristic of multiple streams 140 of the lower gas flow 86 maybe tuned (e.g., by changing the shapes of the multiple dividing walls88, by changing operations of the second gas delivery mechanism 106) tocreate a flow gradient (e.g., gradient in terms of flow velocity or flowrate), such that the upper gas flow 46 and the lower gas flow 86 areefficiently interfaced with one another, and the combination of theupper and lower gas flows 46 and 88 may substantially reduce oreliminate gas entrainment, efficiently removing smoke and/orparticulates from the chamber 20.

With reference to FIGS. 2, 5, and 6, in some embodiments, the multiplestreams 140 may be coupled to the same gas delivery mechanism (e.g., thesecond gas delivery mechanism 106), such that the multiple streams 140are delivered from the same pump or blower 107 and/or through the samefluid valve 105, as illustrated in FIG. 2. Additionally, the one or moreflow characteristics of the multiples streams may be individuallyregulated via different shapes of the multiple pairs of dividing walls88 (e.g., the first pair of dividing walls 142, the second pair ofdividing walls 146, and the third pair of dividing walls 150 of FIG. 6).In some embodiments, the multiples streams (e.g., the first, second, andthird streams 144, 148, and 152 of FIGS. 5 and 6) may be delivered fromdifferent pumps 107 and/or different fluid valves 105, such that the oneor more flow characteristics of the multiple streams 140 may beindividually regulated via applications of the different pumps 107and/or different fluid valves 105 illustrated in FIG. 2. In someembodiments, the flow conditioning device 112 of FIG. 2 may beconfigured to help individually regulating the flow characteristics ofthe multiple streams 140 of FIGS. 5 and 6. For example, the sizes and/orshape of the plurality of openings 114 and/or the thickness 116 of theflow conditioning device 112, as illustrated in FIG. 2 may vary locallyfor the respective flow paths of the multiple streams 140 of FIGS. 5 and6 to individually regulate the flow characteristics.

In some embodiments, the multiple dividing walls 88, the gas deliverymechanism 106, and/or the flow conditioning device 112 are configured oroperated to form a flow gradient. For example, the multiple streams 140closer to the build platform 22, such as the third stream of flow 152,may have a first medium flow velocity. For example, the multiple streams140 slightly away from the platform 22 in the z-direction, such as thesecond stream of flow 148, may have a high flow velocity. For example,the multiple streams 140 closer to the upper gas flow 46 in thez-direction, such as the first stream of flow 144, may have a secondmedium flow velocity. The first medium flow velocity for the thirdstream of flow 152 may be any suitable flow velocity to avoidsignificant disturbance to the powder bed 28, the high flow velocity forthe second stream of flow 148 may be any suitable flow velocity toquickly blow away the smoke and/or particulates, and the second mediumflow velocity for the first stream of flow 144 may be any suitable flowvelocity to avoid gas entrainment due to large flow velocity gradient atthe flow boundary between the upper and lower gas flows 46 and 86. Incertain embodiments, the flow velocity of the multiple streams 140 maydecrease toward the upper gas flow 46 (e.g., the third stream of flow152 has a greater flow velocity than the second stream of flow 148,which has a greater flow velocity than the first stream of flow 144). Incertain embodiments, the flow velocity of the multiple streams 140adjacent to the platform 22, such as the third stream of flow 152, maybe about 8 times the flow velocity of the upper gas flow 46.

FIG. 7 is a flow chart of an embodiment of a method 160 for operatingthe AM system 10. One or more of the steps of the method 160 stored inthe memory circuitry 14 may be executed by the processor 16 of thecontroller 12. Referring to the AM system 10 of FIGS. 1 and 2, themethod 160 includes depositing (step 162) a quantity of a powdermaterial onto the build platform 22 within the chamber 20 of the AMsystem 10. For example, the controller 12 instructs the powderapplication device 26 to deposit the powder material onto the buildplatform 22. The controller 12 instructs the positioning system 36 tomove the powder application device 26 and/or the platform 22 to anysuitable positions relative to one another, in any of the x-, y-, andz-direction, or a combination of, to deposit the powder material in alayer-by-layer manner.

In the illustrated embodiment, the method 160 includes supplying (step164) an upper gas flow into the chamber 20. For example, the controller12 instructs the associated gas delivery mechanism (e.g., the first gasdelivery mechanism 74) to supply the upper gas flow 46 into the chamber20. By way of specific example, the controller 12 instructs theassociated gas delivery mechanism to control the flow characteristics ofthe upper gas flow 46, such as flow distribution, flow rate (e.g., massflow rate, volume flow rate), flow temperature, or any combinationthereof. In certain embodiments, the controller 12 instructs theassociated gas delivery mechanism to control content (e.g., argon,nitrogen, any other suitable inert gas, or a combination thereof) of theupper gas flow 46. In some embodiments, the controller 12 instructs theassociated gas delivery mechanism to supply the upper gas flow 46 intothe chamber 20 simultaneous to step 162.

The illustrated embodiment of the method 160 includes supplying (step166) the lower gas flow 86 into the chamber 20. For example, thecontroller 12 instructs the associated gas delivery mechanism (e.g., thesecond gas delivery mechanism 106) to supply the lower gas flow 86 intothe chamber 20. By way of specific example, the controller 12 instructsthe associated gas delivery mechanism to control the flowcharacteristics of the lower gas flow 86, such as flow distribution,flow rate (e.g., mass flow rate, volume flow rate), flow temperature, orany combination thereof. In some embodiment, the controller 12 instructsthe associated gas delivery mechanism to control the flowcharacteristics of the multiple streams 140 to create a flow gradient(e.g., gradient in terms of flow velocity or flow rate) in the lower gasflow 86. In certain embodiments, the controller 12 instructs theassociated gas delivery mechanism to control content (e.g., argon,nitrogen, any other suitable inert gas, or a combination thereof) of thelower gas flow 86. The controller 12 may instruct the associated gasdelivery mechanisms to control the flow velocities of the upper gas flow46 and the lower gas flow 86, such that a ratio between the two gas flowvelocities is controlled at a desirable value or range (e.g., the flowvelocity of the lower gas flow 86 is in a range between about 10 timesand about 1.5 times the flow velocity of the upper gas flow 46, betweenabout 9 times and about 7 times the flow velocity of the upper gas flow46, about 8 times the flow velocity of the upper gas flow 46). Incertain embodiments, the controller 12 instructs the associated gasdelivery mechanisms to control the flow velocities of the upper gas flow46 and the lower gas flow 86, such that ratios between the upper gasflow 46 and each individual stream of the multiple streams 140 arecontrolled at a desirable value or range. For example, the controller 12may instruct the associated gas delivery mechanisms to control the flowvelocities of the upper gas flow 46 and the lower gas flow 86, such thatthe flow velocity of the upper gas flow 46 is in a range between about0.2 m/s and 1 m/s and the flow velocity of the lower gas flow 86 is in arange between about 2 m/s and 5 m/s. As set forth above, applying thelower gas flow 86 in the chamber 20 (step 166), in combination with theupper gas flow 46 (step 164) may substantially reduce or eliminate gasentrainment and chaotic flow inside the chamber 20 and more efficientlyremove the smoke and/or particulate matter from the chamber 20, whichmay lead to improved quality of the resulting object manufactured by theAM system 10.

The illustrated embodiment of the method 160 includes selectivelyapplying (step 168) a focused energy beam to the quantity of a powdermaterial deposited on the build platform 22. For example, the control 12instructs the energy generating system 30 to apply the focused energybeam 31, such as a laser beam, to portions of the powder bed 28. Thefocused energy beam 31 selectively melts and/or sinters the powdermaterial of the powder bed 28 in a predefined manner to form asolidified layer.

In some embodiments, the steps 164 and 166 may be performedsimultaneously. In some embodiments, the step 164 may be performedbefore or after the step 166. In some embodiments, the step 168 may beperformed simultaneously to the step 164, the step 166, or both. In someembodiments, the step 168 may be performed before the step 164 or beforethe step 166. In some embodiments, the method 160 may repeat the steps162, 164, 166, and 168 to form additional solidified layer on thepreviously formed solidified layer, as indicated by an arrow 170. Insome embodiments, the method 160 may include performing the steps 164and 166 every time after performing the step 168. In some embodiments,the method 160 may include repeating the steps 162, 164, 166, and 168multiple times to form successive additional solidified layers to formthe desired article (e.g., the step 168 is performed while the steps 164and 166 are performed continuously).

The technical effects of the present disclosure include improving theperformance and efficiency of an AM system by removing from the chamber,smoke and/or other particulate matter generated during the AM process.The disclosed AM system employs a combination of an upper gas flowsupplied from a side in the upper portion of the chamber directedparallel to a build platform, and a lower gas flow supplied from theside in the lower portion of the chamber directed toward the buildplatform. The lower gas flow may include one or more parallel streams.The flow velocities of the upper and lower gas flows are tuned withrespect to one another within a desirable range. The combination of theupper and low gas flows, as well as fine tuning of their relative flowvelocities may substantially reduce or eliminate gas entrainment andrecirculation of the smoke and/or the particulate matter inside thechamber.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

The invention claimed is:
 1. An additive manufacturing system,comprising: a housing defining a chamber; a build platform disposed in alower portion of the chamber; a powder application device configured todeposit a bed of powder material on the build platform; an upper gasinlet disposed in a first side-wall and in an upper portion of thechamber and configured to supply an upper gas flow parallel to the buildplatform; a lower gas inlet in the lower portion of the chamber, whereinthe lower gas inlet comprises one or more pairs of dividing wallscontinuously extending from the first side-wall toward the buildplatform and configured to guide the lower gas flow at one or more flowangles with respect to the build platform and wherein at least one ofthe one or more pairs of dividing walls is arranged above the powderapplication device; one or more gas delivery mechanisms coupled to theupper and lower gas inlets and configured to regulate one or more flowcharacteristics of the upper and lower gas flows; and a gas outletdisposed in a second side-wall of the chamber, opposing the firstside-wall, wherein the gas outlet is configured to discharge the upperand lower gas flows from the chamber.
 2. The additive manufacturingsystem of claim 1, wherein a width between at least one of the one ormore pairs of dividing walls narrows along a length of the at least onepair of dividing walls to provide a nozzle effect.
 3. The additivemanufacturing system of claim 1, wherein the one or more flow angles arebetween about 30 degrees and about 1 degree.
 4. The additivemanufacturing system of claim 1, comprising a flow conditioning devicedisposed within the chamber, such that the upper gas flow, the lower gasflow, or both, flow through the flow conditioning device, wherein theflow conditioning device is configured to regulate one or more flowcharacteristics of the upper gas flow, the lower gas flow, or both. 5.The additive manufacturing system of claim 1, wherein the lower gas flowand the upper gas flow are supplied into the chamber at a flow velocityratio that is between about 10:1 and about 1.5:1.
 6. The additivemanufacturing system of claim 5, wherein the flow velocity ratio that isbetween about 9:1 and about 7:1.
 7. The additive manufacturing system ofclaim 6, wherein the flow velocity ratio that is about 8:1.
 8. Theadditive manufacturing system of claim 1, wherein the lower gas flowcomprises multiple streams and each of the multiple streams is guided byone of the one or more pairs of dividing walls.
 9. The additivemanufacturing system of claim 8, wherein the multiple streams aresupplied into the chamber at different respective flow velocities. 10.The additive manufacturing system of claim 8, wherein the multiplestreams comprise: a first stream of flow directly adjacent to the uppergas flow; a second stream of flow at a lower vertical height than thefirst stream of flow; and a third stream of flow at a lower verticalheight than the second stream of flow, wherein the second stream of flowhas a higher flow velocity than flow velocities of the first stream offlow and the third stream of flow.
 11. The additive manufacturing systemof claim 1, wherein the lower gas inlet is disposed at a greatervertical height than the powder application device.
 12. A method ofoperating an additive manufacturing system, comprising: depositing a bedof a powder material on a build platform within a chamber; supplying anupper gas flow into the chamber horizontally above the build platform;supplying a lower gas flow into the chamber toward the build platformvia a lower gas inlet disposed in the lower portion of the chamber,wherein the lower gas inlet comprises one or more pairs of dividingwalls continuously extending from a first side-wall toward the buildplatform that guide the lower gas flow at one or more flow angles withrespect to the build platform, and wherein at least one of the one ormore pairs of dividing walls is arranged above a powder applicationdevice for depositing the bed of the powder material on the buildplatform; and applying a focused energy beam to at least a portion ofthe bed of the powder material deposited on the build platform to form asolidified layer.
 13. The method of claim 12, wherein supplying thelower gas flow comprises supplying the lower gas flow at a second flowvelocity that is between about 10 times and about 1.5 times a first flowvelocity of the upper gas flow, between about 9 times and about 7 timesthe first flow velocity of the upper gas flow, or about 8 times thefirst flow velocity of the upper gas flow.
 14. The method of claim 12,wherein supplying the lower gas flow comprises supplying multiplestreams into the chamber at different flow velocities.
 15. The method ofclaim 12, wherein supplying the lower gas flow comprises supplying thelower gas flow simultaneously with supplying the upper gas flow.
 16. Anadditive manufacturing system, comprising: a housing defining a chamber;a build platform disposed in the chamber; a powder application devicearranged in the chamber and configured to dispose a bed of powdermaterial onto the build platform; an energy generating system arrangedin the chamber and configured to generate and direct a focused energybeam onto at least a portion of the bed of powder material; apositioning system coupled to the build platform, the energy generatingsystem, the powder application device, or a combination thereof, andconfigured to move the build platform, the energy generating system, thepowder application device, or a combination thereof, relative to oneanother; an upper gas inlet disposed in a first side-wall and in anupper portion of the chamber and configured to supply an upper gas flowparallel to the build platform; a lower gas inlet in a lower portion ofthe chamber, wherein the lower gas inlet comprises one or more pairs ofdividing walls continuously extending from the first side-wall towardthe build platform and configured to guide the lower gas flow at one ormore flow angles with respect to the build platform, and wherein atleast one of the one or more pairs of dividing walls is arranged abovethe powder application device; one or more gas delivery mechanismscoupled to the upper and lower gas inlets and configured to regulate oneor more flow characteristics of the upper and lower gas flows; and a gasoutlet, disposed in a second side-wall of the chamber, opposing thefirst side-wall, wherein the gas outlet is configured to discharge theupper and lower gas flows from the chamber.
 17. The additivemanufacturing system of claim 16, wherein a width between at least oneof the one or more pairs of dividing walls narrows along a length of theat least one pair of dividing walls to provide a nozzle effect.
 18. Theadditive manufacturing system of claim 16, wherein the one or more flowangles are between about 40 degrees and about 1 degree or between about30 degrees and about 20 degrees.
 19. The additive manufacturing systemof claim 16, wherein the lower gas flow and the upper gas flow aresupplied into the chamber at a flow velocity ratio that is between about10:1 and about 6:1, between about 9:1 and about 7:1, or about 8:1. 20.The additive manufacturing system of claim 16, wherein the lower gasflow comprises multiple streams and each of the multiple streams isguided by a particular pair of dividing walls of the one or more pairsof dividing walls.
 21. The additive manufacturing system of claim 16,wherein the multiple streams are supplied into the chamber at differentflow velocities.
 22. The additive manufacturing system of claim 16,wherein the lower gas inlet is disposed at a greater vertical heightthan the powder application device.